Negative impact of butyric acid on butanol recovery by pervaporation with a silicalite-1 membrane from ABE fermentation

Abstract In this study, the utilization of silicalite–1 membrane pervaporation for butanol recovery from an acetone-butanol-ethanol (ABE) fermentation broth solution was investigated. In particular, the negative effect of butyric acid on the pervaporation performance was tested. The presence of butyric acid was observed to decrease both the butanol flux and selectivity of the membrane. Clear relation between the severity of the decreased performance and the amount of butyric acid was observed. Increasing the pH of the feed solution was observed to improve butanol pervaporation in the presence of butyric acid. In pervaporation of ethanol, butanol and butyric acid, there are significant interactions in adsorption and diffusion between the components. The presence of butanol restricts the permeation of ethanol while the butanol permeation is restricted by the presence of butyric acid. The effects likely arise from adsorptive competition and are further amplified due to the rates of diffusion. In addition, butyric acid exposure may change the membrane properties over time, although they may be restored by heating. The results suggest that the selective recovery of butanol with a silicalite–1 membrane is not feasible if the concentration of butyric acid is significant and the pH value in the solution is low